The present invention relates in general to a lid having a radiation transmissive window and, more particularly, to such a lid having adjacent the window an opaque layer with an aperture therethrough.
An existing device includes a housing with an opening therein which is closed by a lid, the lid having a frame and having a window which is hermetically sealed to the frame, the window being transmissive to radiation in a waveband of interest. A chrome layer is provided on one side of the window, and has therethrough a generally rectangular aperture with straight sides and slightly rounded corners. The device includes within the housing a digital micromirror device (DMD) of a known type.
A beam of radiation enters the housing through the window in the lid, and is processed by the DMD to form a plurality of sub-beams. Some of the sub-beams then exit the housing through the aperture and window, in order to facilitate generation of an image which is projected onto a screen, for example in a television or a movie theater. Although known lids of this type have been generally adequate for their intended purposes, they have not been satisfactory in all respects.
In this regard, when the sub-beams that exit the housing through window and aperture form a projected image on a screen, this image is typically -surrounded by a border region which is intended to be relatively dark. However, a noticeable line or zone of bright light sometimes appears within the dark border region. In some cases, two or more of these undesirable lines or zones of light appear at the same time. These undesirable lines of light were believed to be caused in some way by the known lid, although there was no clear understanding of exactly how the lid might be causing this problem.
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus involving a lid that avoids undesirable regions of illumination in the border around a projected image. According to a first form of the present invention, a method and apparatus are provided to address this need, and involve: providing a window which is transmissive to radiation of a predetermined wavelength and which has a surface thereon; providing adjacent the surface on the window a layer which is nontransmissive to radiation of the predetermined wavelength, and which has an aperture therethrough; and configuring an edge of the layer that extends around the circumference of the aperture to have a slope which extends at an acute angle greater than approximately 15xc2x0 with respect to the surface on the window.
According to a different form of the present invention, a method involves: providing a window which is transmissive to radiation of a predetermined wavelength and which has thereon a surface with first and second portions; forming a layer of a positive photoresist material on first and second portions of the surface; removing a selected portion of the photoresist material on the first portion of the surface so as to leave a remaining portion of the photoresist material on the one-second portion of the surface; applying over the remaining portion of the photoresist material and over the first portion of the surface a layer of a further material which is nontransmissive to radiation of the predetermined wavelength, including application of the further material in directions other than perpendicular to the surface so that the further material on the first portion of the surface has an edge portion which is adjacent to and extends around the remaining portion of the photoresist, and which is sloped to extend at an acute angle greater than approximately 15xc2x0 with respect to the surface; and thereafter removing the remaining portion of the photoresist material and the portion of the further layer thereon, so as to leave through the further material an aperture which has the edge portion of the further layer extending along a circumference thereof.